President Obama has said that he will act administratively on immigration before the midterm election. Pro-immigration activists are pleading with him to "go big and bold," as Gustavo Torres, executive director of CASA de Maryland, told BuzzFeed. If Obama is in a gambling mood, he might do just that.

Big and bold action would presumably entail an extension of the administration's deferred action policies, which currently protect young immigrants from deportation, to other family members or other classes of settled undocumented immigrants. Government shouldn't be in the business of "tearing families apart who otherwise are law-abiding," Obama has said. (The influx of unaccompanied Central American children at the border is a different issue altogether, but Obama needs to show progress stemming the tide of children before liberalizing immigration rules for others.)

Any executive action of that breadth would produce high-pitched wails from nativists along with calls for impeachment from those Republicans too decorous to demand that Obama be drawn and quartered. It would roil Congress, raise constitutional concerns about executive overreach, give Republicans more fodder for attacks and inject "amnesty" into key congressional campaigns.

All of which might not be the worst outcome, from Obama's point of view.

There is no guarantee that Democrats will lose their Senate majority in November. But if the current political trajectory holds, Republicans may well win the additional six seats necessary for the Senate to change hands. A narrow Republican Senate majority will probably be a nightmare for Republican leader Mitch McConnell of Kentucky, who may have to mortgage the last vestiges of Republican probity to the demands of in-house ideologues and a base split between a faction hunkering down in the 1980s and one fleeing for the 1890s.

It wouldn't be a picnic for Obama, either. While Republicans would have enormous difficulty cobbling together a coherent legislative agenda, in between fishing expeditions and scandal mongering, they would wage constant attacks on environmental legislation and the funding and structure of the Affordable Care Act. And they would sometimes succeed.

A major executive action liberalizing strictures on undocumented immigrants with lengthy U.S. residency would change the midterm dynamic. Experience suggests that the reaction of Rep. Steve King and other Republican nativists would not be subtle. And Republican leaders, including McConnell and House Speaker John Boehner, would add to the general clamor. Conflict over immigration would become much louder and more heated, and the issue might well dominate some campaigns.

The conservative base is already motivated; the threat of liberalized immigration policy seems unlikely to add greatly to Republican vote tallies. But in some states with tough Senate races — Georgia and North Carolina, for example — a knockdown national fight over immigration might impel more Hispanics and Asians to vote, while heightened attacks on Obama could rally more black voters, whose devotion to the president was tested, and reconfirmed, in 2012. In a tight race, Hispanics and Asians might make a measurable difference; black voters could make a decisive one.

The biggest challenge facing Democratic candidates in 2014 is arguably not Obama fatigue, disgust with Washington or frustration with an economy that simply does not reward unskilled work. It's the concentration of Senate races in conservative states and the drop-off of traditional Democratic constituencies, who typically fail to vote in large numbers in midterm elections.

Not every Democratic voter would be comfortable with amnesty for more undocumented immigrants. Some genuinely independent voters might be turned off as well. But a high-stakes, high-drama pre-election fight between Obama and Republicans might motivate more Democrats to vote while promoting immigration policy that Obama prefers to the status quo.

If Republicans subsequently take the Senate, the consequences for Obama would surely be ugly. But they would be pretty ugly even without his becoming the champion of undocumented immigrants. If Obama goes small, he disappoints his base and may well end up with a Republican Senate anyway. If he goes big, he probably locks in a huge, long-term Democratic advantage among Hispanic voters — and possibly holds the Senate. In effect, by risking a slightly more miserable 2015, Obama could gain a significantly less miserable one. Even if that fails, he would still strengthen the Democratic claim on Hispanic voters.

A famous defense intellectual once said: "If you can't solve a problem, make it bigger." Facing inaction on immigration and the yawning abyss of a hostile Republican Congress, Obama might see some wisdom in that.

Francis Wilkinson writes editorials on politics and domestic policy for Bloomberg View.