* The endgame: So it’s come to this: With the debt ceiling impasse entering its final and decisive phase, both sides seem to be completely convinced that the other side will be the one that ultimately caves in the end.

In the past 24 hours, Harry Reid and John Boehner have both managed to build substantial support for their own positions, with the result that each is more convinced than ever that the standoff is heading his way. In the House, John Boehner’s two-tiered debt ceiling hike proposal seems more likely to pass when it’s voted on today than it did yesterday morning, now that some prominent House conservatives are saying nice things about the bill, and freshman GOPers seem to be breaking in favor of it.

Passage is not assured — a comprehensive whip count finds that 22 House GOPers are firm No votes or are leaning No — and defeat would be a crushing blow to Boehner’s leadership. But the count also shows that the proposal is picking up Yes votes, and most observers think it will squeak through.

Meanwhile, in the Senate, Dem leaders were buoyed by a letter signed by all Senate Democrats vowing to vote down Boehner’s plan in that chamber. Dem leaders are convinced that the certain defeat of Boehner’s proposal in the Senate will increase pressure on Republicans to come around to Reid’s proposal as the only way to avoid getting blamed for default and economic catastrophe.

So how does this end?

* Senate Dems game out their strategy: With Boehner’s proposal seemingly set to pass, Senate Dems are mulling three options: First, don’t vote on Boehner’s bill at all, which would anger GOP senators. Second, vote down Boehner’s bill and try to pass Reid’s proposal, using the failure of the Boehner bill to exert pressure on GOP Senators to support Reid’s. And third, vote down Boehner’s plan and try to pass a compromise version of Reid’s plan negotiated with Mitch McConnell and also with Boehner, so it can hopefully pass the House once it’s kicked back to that chamber.

As best as I can determine, option three is the most likely. The key questions: Whether there is ultimately any kind of compromise proposal that can pass the House; how much Dems are willing to concede to make that happen; and how much spine Dems are willing to display right up to the drop-dead moment in order to force House Republicans to move in their direction.

* Can GOP accept the Dems’ bottom line? Major Garrett tells Republicans that they will ultimately have no choice but to swallow a single debt ceiling increase, because Obama and Dems will never give on this point. Tempting to believe, but I’m not so sure.

* Reality check of the day: As Stephen Stromberg notes, the fact that some compromise version of Boehner’s deeply unpopular plan is most likely to pass shows you how far to the right of public opinion the debate in Congress has shifted.

Key takeaway: Even if the final compromise is closer to Reid’s plan than to Boehner’s, the outcome will constitute a major victory for the right.

* Dems to renew push for “Constitutional option”: House Dems will renew their push at a press conference today for President Obama to “invoke the 14th Amendment” to “raise the debt ceiling and avoid national default,” according to a press release. The pressure reflects a growing sense among some Dems that the outcome to the debt ceiling impasse will be an absolutely terrible deal along the lines of Boehner’s proposal — and that’s the best case scenario.

* Boehner’s dilemma: Congressional expert Norm Ornstein gets to the heart of it:

Boehner and his leadership team are pulling out all the stops, putting his full prestige on the line, to get members to renege on their ironclad pledges. Every speaker has these moments when getting to a bare majority is excruciatingly difficult, and it requires offering inducements or simple begging. But a speaker can only go to the well once or twice to get his or her members to walk the plank. In this case, Boehner’s tactical maneuvers mean that he is asking two dozen or more of his colleagues to walk that plank in return for something that has no chance of becoming law.

* But is Boehner’s job really in jeopardy?It’s been a given among many on the left that the Speaker will have to seriously watch his back if a debt ceiling compromise passes that isn’t 100 percent acceptable to the Tea Party. But Carl Hulse surveys Republicans and concludes few would have the stomach to try to oust him.

* Report: Obama is NOT taking his base for granted: Peter Wallsten reports that the White House is waging an unusually aggressive behind the scenes campaign to reassure liberal activists and core Dem constituencies who are upset that Obama has given too much ground in the debt ceiling fight. It’s a sign that the White House may recognize that anger on the left could pose a serious problem for the reelection campaign.

* Conservatives got crushed in the Medicare debate: Here’s some of the best evidence yet: The conservative American Action Network is running ads targeting House Democrats by claiming their Medicare plan would “balance the budget on the backs of seniors.”

The fact that conservatives have been reduced to appropriating the exact same language Dems have used against Republicans is the clearest sign yet that they got destroyed in the rhetorical war over Medicare’s future.

* What we call “centrism” is completely arbitrary: As E.J. Dionne spells out today, there’s no percentage in Obama making a bid for the political “center,” since such a place doesn’t really exist; he’s better off returning to the core reasons he wanted to become President in the first place.

* And liberals have long gotten played for chumps by deficit hysteria: The right has a long history of using deficit hysteria to attack the social safety net, and liberals have a long history of playing along.

What else is happening?