1. Today’s reality check: read Andrew Gelman on what it really means to say that Barack Obama has a 60 percent or 75 percent chance of winning.

2. Into the weeds on possible reasons the results might not match the polling: Sean Trende believes there’s an impossible mismatch between state and national polls.

The most important polling number of the day? I’ll vote for Tammy Baldwin leading Tommy Thompson, 47 percent to 43 percent, in polling from the very well-regarded Marquette Law School team.

Not only is that bigger than the 3.1 percent lead Baldwin had previously held in the HuffPollster average, but Marquette’s previous survey had supplied Thompson with his only non-Rassmussen lead since Baldwin moved into the polling lead in September.

Why is this a big deal? First of all, because it means that there’s a very good chance that Tammy Baldwin is going to be a United States Senator. There’s some symbolic importance for her as an open lesbian getting elected to the Senate. But perhaps a bigger deal is that there’s every expectation that she will be an active, hard-working liberal in a chamber which often seems to have few of those. Individual Senators can make a great deal of difference. Influence depends to a large extent on the Senator’s abilities, not (as in the House) their committee or leadership position.

But party majority (and the size of the majority) matter quite a bit as well, and that’s the other reason this poll, and the implication that Baldwin is in pretty good shape, matter quite a bit. Wisconsin has been ranked as the Democrats’ 51st Senate seat: that is, there were 50 seats with either a Democrat incumbent who isn’t running or a Democrat currently winning by more than Baldwin’s 3.1 percent. Subjectively, I’ve always thought she was more likely to fade than some of the other “lean Democratic” leaders, such as Elizabeth Warren in Massachusetts or Sherrod Brown in Ohio. But that doesn’t seem to be the case (perhaps because Tommy Thompson has proven an awful candidate for this cycle).

In other words, this poll, along with the other evidence of the last several days, make it highly unlikely that Republicans can win back the Senate. And don’t forget: In addition to the 51 Senators Dems will have if they hold their current clear leads, there are another three tossup states (Virginia, Montana, and Indiana) where Democrats currently hold apparent polling leads, and four others (North Dakota, Arizona, Nevada, and Nebraska) where Republicans have small leads. It’s now probably more likely than not that Democrats will at least retain 53 seats in the new Senate, and they could easily have more.

In all, it’s shaping up to be an excellent cycle for Democrats in the Senate; we’re close to the point where the only question is how excellent it will be.

Here’s another reason to be cautiously optimistic about the way the political winds are blowing: With Dems seemingly on track to hang on to the Senate — and with Obama’s electoral edge perhaps holding — the prospects are brightening for an overhaul of the filibuster.

Senator Jeff Merkley, the co-author of a package of filibuster reforms, has secured commitments from nine leading Dem Senate candidates to throw themselves behind fixing the filibuster if they are elected.

Merkley is circulating an email raising money for the nine Senators, who include Elizabeth Warren, Tammy Baldwin, Martin Heinrich, Tim Kaine and Heidi Heitkamp. “These nine candidates running for the Senate right now have committed to helping me fix the broken Senate by reforming the filibuster,” the email says.

If Dems do hold the Senate, we could be looking at a more progressive Democratic caucus next year, thanks to this year’s crop of unexpectedly solid progressive candidates. This could result in more pressure on the Dem leadership to actually go through with reform.

Merkley is calling for reforms that, among other things, would force the filibustering party to play a much more public role in obstructing the majority — perhaps making it politically less appetizing. The Senate has already adopted one proposed reform, the elimination of the secret hold.

This spring, Harry Reid caused a stir when he said he’d finally seen the light on the need for real reform. Republicans are skeptical that Reid is serious about changing the filibuster, and there’s some grounds for that skepticism. However, it’s also possible that the unprecedented GOP obstructionism of the last four years may have persuaded Reid, as David Dayen put it recently, that the Senate has become a “super majority institution” that is “governed by a tyranny of the minority” and is “horrendously broken.”

Obviously Mitt Romney could still be elected president, and take along enough Republicans to give GOP control of the Senate. If Dems lose the White House and hold the Senate, their appetite for filibuster reform may well diminish. But if Dems hold both the White House and the Upper Chamber, reform may become a real possibility. It would be an ironic outcome if the very plot hatched by GOP leaders to deny Obama a second term — abusing the rules and rendering the institution dysfunctional to turn his presidency into a failure — is what finally created the political will among Dems to take steps towards ending such dysfunction and abuse for good.

President Obama’s achilles heel in this election is his performance with white voters. If he falls below 40 percent, his prospects for reelection are endangered. Given the tight race Iowa, and the seemingly tight race in Michigan, one theory is that Obama has slipped below the critical mark for white support. It’s part of the reason the Romney campaign is loudly touting its efforts to “expand” the electoral map and put President Obama on the defensive in several key states. To wit, the Restore Our Future Super PAC has launched a $1.8 million ad buy in Minnesota and New Mexico — two relatively safe states for Obama — and the Romney campaign itself has made moves in Pennsylvania, Michigan, and Wisconsin.

Unfortunately for Team Romney, a poll released this afternoon, from Marquette Law School, throws a little water on this theory. In Wisconsin, Marquette — one of the most reputable pollsters in the state — shows Obama with an 8 point lead over Romney, 51 percent to 43 percent.

Still, this is only one poll, and others show a closer race in core Democratic states. A Detroit News poll has Obama with just a 3 point advantage in Michigan (48–45), a Mason-Dixon poll has him with a similar advantage in Minnesota (47–44), and a Pennsylvania poll from Franklin & Marshall shows Obama ahead by 4 points (49–45) in a state that he won by double-digits in 2008.

If these polls are an accurate picture of the race, then we’re looking at a fundamental shift in the election. A world where Obama is falling behind in blue states like Michigan and Minnesota is one where his support among white voters is actually collapsing.

But judging from the polling averages, Marquette — which implies steady performance with white voters — seems generally closer to the mark. In states with similar demographics to Wisconsin, Obama is still leading. In In Minnesota, Obama has a 6.9 point lead over Romney; in Michigan, it’s also 6.9 points; in Pennsylvania, it’s 4.9 points; and in Wisconsin, it’s 4 points, with Obama breaking 50 percent.

As with last week’s “momentum” narrative, Team Romney’s declaration that they are “expanding the map” has more to do with perception than reality. Barring something catastrophic, there’s no way Romney can close the gap in Minnesota or Michigan. Indeed, far from showing confidence, Romney is revealing the extent to which he’s worried about his path to 270 electoral votes.

The most valuable state on the board is Ohio, Without it, Romney has to run the table everywhere to win the presidency. And so far in the state, Obama has maintained a small but resilient advantage — a 2.4 point lead according to the Pollster average, and an identical one in the Real Clear Politics average. Doing something as simple as taking a median of the most recent polls — which drops the outliers from consideration — leaves you with an Obama lead of 2.5 points.

If Romney had leads in Virginia and Colorado, things would look a little different, but he doesn’t. The contest in both states is a dead heat. Romney is aching for a secure path to the presidency, and his push to “expand the map” is a clear sign he doesn’t have one.

Jamelle Bouie is a staff writer at The American Prospect , where he writes a blog .

With polling averages showing that Obama holds a small but meaningful edge in the electoral college in enough states to put him well past 270, Republicans have fallen back on a prediction: A last minute shift in the electorate will put Mitt Romney over the top.

As Mike Allen put it this morning, many Republicans “fear Romney’s momentum has stalled” and are now banking on “some tectonic shift in the country hasn’t been fully detected by pollsters or explained by the press.” This is a variation of the other argument Romney supporters have been making for some time — that a last minute break Romney’s way will ensure another outcome like 1980.

The question, though, is whether the rise in early voting is making this scenario more and more remote.

On a conference call with reporters, David Axelrod derided the “myth of the wave that it’s all going to break in his favor.” He added: “This professed momentum from the Romney campaign is really faux-mentum.”

Obama advisers cited two factors that they say makes the “last minute wave” theory bogus. They argued that Obama’s early voting edge all but ensures that Romney needs to rack up massive margins among the remaining voters. If this is so, it makes the “last minute wave” theory less and less plausible.

Obama campaign manager Jim Messina told reporters that campaign calculations show that Obama’s lead in early voting in North Carolina, Nevada, and Iowa mean that Romney has to win from 54 to 60 percent of the election-day vote in those states to prevail.

The idea that early voting reduces the chances of a last minute tectonic shift is one that hasn’t gotten enough attention, and is worth thinking about.

Axelrod also made a case against the wave I hadn’t heard before: He said undecided voters in the battleground states are tilting towards Obama. “In many of these states, look at structure of undecided vote that remains,” Axelrod said. “They almost uniformly have a more positive view of the President than they do of Governor Romney.”

I’m double checking to see if the data bears that out. For now, keep in mind what Axelrod said the other day: In six days, we’ll know who’s bluffing.