Via RCP. Given the state of separation of powers in year seven of Hopenchange, prosaic reminders like this one that Congress has a role to play in approving major international agreements actually do qualify as newsworthy, especially coming from a Democrat. Not all that surprising coming from Kaine, though: He was also a rare example of Democratic resistance to Obama’s plan to wage war against ISIS without congressional authorization. That resistance eventually led O to ask Congress for an (admittedly meaningless) AUMF.

Kaine’s not the only Senate Dem who’s a potential thorn in Obama’s side either. One of the big knocks on Tom Cotton’s Iran letter was that, by irritating Democrats, it jeopardized the bipartisan skepticism in the Senate about the nascent terms of the Iran deal. Politico talked to a bunch of Senate Dems over the weekend, though, and found they haven’t budged, Cotton or no Cotton:

Though several Democratic senators told POLITICO they were offended by the missive authored by Sen. Tom Cotton (R-Ark.), none of them said it would cause them to drop their support for bills to impose new sanctions on Iran or give Congress review power over a nuclear deal…

“The letter’s incredibly unfortunate and inappropriate,” said Sen. Heidi Heitkamp of North Dakota, a centrist Democrat who voted for the sanctions bill in committee and is a sponsor of the congressional approval legislation. “That doesn’t diminish my support for the legislation that we introduced.”…

Though the White House has seized on the GOP’s “open letter to the leaders of the Islamic Republic of Iran” in an effort to shift the politics of the nuclear negotiations in its favor on Capitol Hill, there’s no evidence it’s working so far. Nearly all of the 54 Republicans and more than a dozen Democrats in the Senate remain at odds with the president on the issue…

Another bill, proposed by Sen. Mark Kirk (R-Ill.), could also be an option if Congress begins to doubt Iran’s commitment to finalizing a deal or upholding one. Kirk’s bill would trigger sanctions if Iran walks away from talks or reneges on a deal. He said 68 senators have signaled support for it, a number he predicted would grow “once we actually vote.”

It’s a testament to how much Democratic opposition there is to the deal that the White House has begun to admit that Congress has a role to play in approving it. Obama’s chief of staff, Denis McDonough, acknowledged that in a letter to Bob Corker over the weekend. That too should be prosaic: Of course Congress has a role to play in lifting sanctions that were imposed by Congress, a point made by Kaine in the clip. Ask yourself, though, how different Obama’s reaction would be if this were a strictly party-line vote in the Senate instead of a bipartisan, possibly veto-proof majority ready to humiliate him by tanking his deal. The narrative then would be “Republican obstructionism,” not “we respect Congress’s part in this.”

What Obama and McDonough are asking for right now is time. They want to finish negotiations with Iran before Congress passes a bill and formally takes up the matter; if the Senate started rumbling right now about rejecting it, Iran might walk away. They also want time to twist the arms of Senate Dems who are momentarily voting with the GOP. Obama’s reconciled himself to the fact that he’ll be humiliated by members of his own party on this when Congress eventually votes on sanctions. If he can hold McConnell below the 67 votes needed for a veto-proof majority, though, at least he can preserve his “executive agreement” for the rest of his term. As for the minor problem of needing Congress’s approval to lift sanctions, if you read the fine print you’ll see that current sanctions laws allow O to unilaterally waive sanctions for six months at a time. Presumably he’d use that option to give Iran some relief. And even if U.S. sanctions remained in place, striking a deal with Iran would give America’s European partners cover to relax their own sanctions, which might be sufficient to keep Iran onboard, at least in the early stages.

The irony of this Democratic mini-rebellion in the Senate is that it’s being driven by one of Cotton’s main points in his open letter to Tehran. Obama has less than two years left in office, he reminded the mullahs, whereas some of us in the Senate have close to six years. Don’t think that fact’s not swimming around in the minds of red-state Dems like Joe Manchin and Heidi Heitkamp — and Tim Kaine — who’ll have to answer for this in 2018 while Obama’s enjoying his new semi-pro golf career. The Iran deal, with its 10-year timeline for compliance, is a grand punt by the White House to the next administration, but it’s not just the next president who’ll be receiving that punt. If the deal goes as badly in practice as everyone expects, Senate Dems will get tackled before any Republicans will.