ENTERING HIS last year in office, Virginia Gov. Robert F. McDonnell (R) faces the starkest choice of his four-year term: Does the governor want to be remembered as a problem-solver who finally tackled a multibillion-dollar transportation crisis, thereby ensuring the state’s prosperity? Or does he prefer to be known for rubber-stamping a hyper-partisan power grab by Republicans who used legislative skulduggery and cartographic trickery to seize control of what had been an evenly divided state Senate?

Mr. McDonnell, a Republican, cannot have it both ways. And if, as is widely assumed, he has presidential aspirations in 2016, the question is really one of identity. In the final analysis, is the governor a pragmatist or a political hack?

That Manichaean choice has been forced on him by his fellow Republicans in the Senate, who, taking advantage of the one-day absence of a single Democratic senator last Monday, rammed through a new electoral map without a single public hearing, let alone anything resembling genuine debate.

The map redraws Senate districts in a way designed to tilt a half-dozen currently held by Democrats into Republican hands. It would almost certainly result in a GOP-dominated Senate alongside the already GOP-dominated House of Delegates. What’s more, it’s racially suspect. It would pack African Americans into a newly drawn district in Virginia’s Southside, thereby yielding an additional black senator. But in the process it would redistribute concentrations of black voters elsewhere, reducing the influence of African Americans overall.

It’s hard to believe Mr. McDonnell wants to stain his legacy with such a map. Early in his term, he moved quickly to correct his mistake after he issued a proclamation on Confederate history with no reference to slavery. Why would he revive the issue of racial insensitivity as he prepares to leave office?

Mr. McDonnell said he had a low opinion of the Senate Republicans’ maneuver, but he has not said whether he will allow the the gerrymander to become law. If he does, he should expect retaliation from Senate Democrats, who have already promised to torpedo the governor’s legislative agenda if the new map is foisted on them.

That agenda includes major reforms for public schools and an overhaul of Virginia’s transportation funding system now scheduled to run out of money for new road projects in four years. The governor’s transportation proposal, in particular, would form the centerpiece of his four-year term; given the failure of his predecessors to find a fix, it would be a monumental achievement.

To jeopardize that to score a partisan victory would be foolish and an uncharacteristic departure for a governor who, by instinct and temperament, has governed mainly from the center, avoiding gratuitous partisan brawls. To redefine his governorship now, and reshape his legacy, would only hurt his own political prospects — and leave behind a venomous political residue in the state he has served for many years.