The GOP has a real shot to take control of the Senate next year. Democrats are defending a lot of right-leaning turf, while nearly every Republican up for re-election comes from a solidly conservative state.

But before 2014 comes, Republicans have to answer a key question. What do they want more: Shutdown '13 or Senate '14?

They can't have both.

While Republicans have a good chance to fully control Congress, a lot of things have to go right for them. Their rosy political prospects do not stem from the public's deep love of Republicans, or a dramatic ideological pendulum swing driven by a revulsion of President Obama. Consider that only 25 percent of the country approves of the GOP's handling of Congress and 48 percent says the Republican Party is "too extreme."

The reason why Republicans may have a good 2014 is that the Senate is a body designed by our founders to provide affirmative action to rural, low-population states, which presently lean more to the right than the rest of the country. And several of these states are represented by Democrats up for re-election next year.

Of course, these toss-up states — namely, Alaska, Arkansas, Iowa, Louisiana, Montana, and North Carolina — are not so conservative that a moderate and/or populist Democrat can't beat a right-wing and/or scandal-tainted Republican. After all, Democrats are in those Senate seats right now.

Republicans will need a net gain of six seats to win control of the Senate, presuming that New Jersey's October special election will send a Democrat to replace Gov. Chris Christie's Republican seat warmer. Two other contests for open seats currently in Democratic hands — South Dakota and West Virginia — will almost surely turn red. So Republicans likely need to win four out of the six toss-ups. That seems very doable...

...unless Republicans go all in on a federal government shutdown. It really might happen on Sept. 30 if Congress cannot forge a bipartisan budget agreement before the current law funding the government expires. That would be a self-inflicted wound for the entire party, harming Republican chances across the board.

Such a reckless act would re-confirm the Republican Party caricature as a rogue gang of extremists unserious about governing and uncaring about inflicting pain for ideological gain. It would sap the case for a Republican takeover, and give Democratic incumbents the ability to distance themselves from Washington dysfunction.

Congressional Republicans already tried to play the shutdown game in 1995 and got burned badly. By a nearly two-to-one ratio, voters blamed the Republicans and not President Bill Clinton. Democrats gained a 7-point swing in polls asking party preference for Congress.

Why couldn't Republicans make the president take the blame for a shutdown on his watch? As former House Majority Leader Dick Armey has explained, "Republicans get blamed for shutdowns. It's counterintuitive that Democrats who love government would shut it down."

Inadvertently proving the point, Sen. Ted Cruz (R-Texas) is now practically cheering for a shutdown as evidence that the government doesn't do much. This week he said, "There are some Democrats, some in the media, and some Republicans who portray a shutdown as a horrible calamity. [But] every single week on the weekend, Saturdays and Sundays, we see temporary partial government shutdowns, and the world doesn't end."

Cooler heads in the Republican leadership may yet prevail. According to Politico, Speaker John Boehner reportedly told his caucus this week that beyond conceding the Senate, "Republicans could even lose the [House] majority if they shut down the government." That may be a bit alarmist; the 1995-96 shutdown did not help Republicans, but it did not cause them to lose Congress either. But you might think a rational conservative might not want to take the risk of giving Obama an extra two years to pursue his legislative agenda freed from Republican roadblocks.

However, possessing a modicum of political sanity won't account for much if Republican leaders can't whip their caucus to vote for a budget compromise. Just this week House leaders had to yank off the floor a transportation and housing spending bill of their own making because Republicans fractured when faced with voting for specific, deep cuts. Forcing party discipline over a bipartisan budget deal won't be any easier, especially when Tea Party calls for shutdown are growing louder and primary challengers like Kentucky's Matt Bevin are pressuring incumbents to reject any concessions.

Making matters worse for Boehner, Republican disunity combined with self-awareness of their political fragility equals diminished leverage. Democrats can, for example, insist on additional tax revenue, knowing they will either get Republicans to swallow that revenue or choke on a shutdown.

In other words, if Republicans want the Senate, they are going to have to pay a price for it.