The walls seem to be closing in on the Obama presidency.

Iraq and Syria are overrun with terrorists. Violence is flaring in Ukraine and on Israel’s borders. A humanitarian crisis is developing on our own southern border, but immigration legislation, like most all legislation, is moribund. Probes of the veterans’ health-care system, the IRS and Benghazi are sucking up attention and the administration’s time.

As President Obama fails to get any credit for the millions who have found jobs or gained health-care coverage on his watch, a nonpartisan Quinnipiac poll this week found that 33 percent of Americans consider him to be the worst president since World War II, besting (or worsting, as it were) George W. Bush and leaving Jimmy Carter and Richard Nixon in the dust.

No wonder this bear wants to break loose. And maybe he will — if Republicans take control of the Senate.

Crazy talk, you say? Maybe so. The prevailing view is that a Republican Senate would only compound Obama’s woes by bottling up confirmations, doubling the number of investigations and chipping away at Obamacare and other legislative achievements.

Yet there’s a chance that having an all-Republican Congress would help Obama — and even some White House officials have wondered privately whether a unified Republican Congress would be better than the current environment. Republicans, without Harry Reid to blame, would own Congress — a body that inspires a high level of confidence in just 7 percent of Americans, according to a Gallup survey last month finding Congress at a new low and at the bottom of all institutions tested.

There would be no more excuses for Republicans’ failure to put forward their own health-care plan, immigration proposals, specific cuts to popular government programs, and pet causes involving abortion, birth control and gay rights. This would set up real clashes with Obama — who could employ the veto pen he hasn’t used a single time since Republicans gained control of the House in 2010 — and sharp contrasts that would put him on the winning side of public opinion.

It is not hard to imagine a Republican takeover of the Senate causing conservatives in both chambers to overreach. House Republicans would get more pressure from their base to take a swing at impeachment, because the odds of convicting Obama in the Senate would be better (if still prohibitive). Alternatively, Republican leaders, recognizing that the public will hold them responsible now that they have complete control of Congress, might try to compromise with Obama.

In the first scenario, marauding conservatives drive Republicans to oblivion in 2016 and beyond, putting Hillary Clinton in the White House. In the second scenario, Obama actually accomplishes something in his last two years.

Of course, there is a third scenario, in which a Republican Senate majority only makes Obama miserable. Norm Ornstein , Congress watcher nonpareil, predicts Republicans would halt executive-branch confirmations, leaving the administration weak and understaffed. Remaining staffers would be hamstrung as they try to comply with a new wave of congressional subpoenas. And Republicans may content themselves simply to keep the legislative process shut. “Luring them into a further layer of craziness has advantages,” Ornstein said, but “the danger for Obama is what resonates with the public is he’s the president: Why the hell can’t he get it done?”

A unified Republican Congress could also force Obama to accept rollbacks of Obamacare and other Democratic achievements by attaching the rollbacks to must-pass legislation. Michael Tomasky argued in the Daily Beast that a Republican majority would “take as many bites as it can out of what Obama has accomplished in the last six years.”

Such concerns are all valid, but they may not give enough weight to conservatives’ tendency to overplay their hand, as Sen. Ted Cruz (Texas) did by provoking last year’s government shutdown or as Rep. Darrell Issa (Calif.) has done with a stream of wild accusations that discredited his investigations.

I hold out hope that a Congress under unified Republican control might react the way it did during Bill Clinton’s presidency, producing a balanced budget and welfare reform. But if Republicans don’t take seriously their responsibility to govern, they’ll find the Senate even less governable than it is today. Democrats would still have more than enough votes to block legislation with filibusters — as the Republican minority did in the last two years of Bush’s presidency.

But hopefully Democrats would let some of the more egregious proposals reach Obama’s desk. Of the 2,564 presidential vetoes since 1789, this president has issued only two, both over obscure issues. More exercise of the veto pen could strengthen Obama’s weak hand.

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