Don’t be fooled by the bravado you may hear from Republicans saying they’re delighted that Tim Kaine has declared his candidacy for the U.S. Senate in Virginia in 2012. As they surely know, he instantly becomes the race’s favorite, for a range of reasons the GOP will have a hard time combatting. If they think they’ll win a race for the U.S. Senate talking about highway rest stops, guess again.

Kaine does have an Achilles heel, but it’s beyond the reach of Virginia Republicans to exploit directly. As President Obama’s hand-picked head of the Democratic National Committee, he is as or more closely tied to the man in the White House than just about any other Senate candidate could be.

But the president’s own fortunes depend largely on how the economy looks heading into election season more than a year from now. If the economy double dips, Obama’s in trouble and so in Kaine. If the recovery continues or gains speed both men will be hard to beat in a state the president carried in 2008. This far out, that’s an imponderable.

Sure, Republicans will try to tar Kaine by talking about the 19 highway rest stops he closed to cut costs. But that will wear thin fast in a race where jobs, the deficit, and two or more wars are in the mix. A candidate much dimmer that Kaine could make quick work of a Republican Senate campaign that turns on the number of toilets on I-95.

Then there’s the question of the tax increase Kaine proposed as he prepared to leave office in early 2010. No doubt, tax increases weren’t popular at the time--and his was quickly thrown out by the General Assembly and his successor in the governor’s mansion, Robert F. McDonnell.

But it’s also crystal clear that McDonnell simply shuffled the pain into the future by withholding, in his first year in office, the state’s $620 million contribution to Virginia’s pension fund--a sum the state must now pay back. Will the Republicans’ pay-me-later plan really trump Kaine’s pay-me-now plan? I doubt it.

Republicans were also fond of slamming Kaine for taking the helm of the DNC in his final year as governor, thereby neglecting his duties in Richmond. There may be something to that. But how much traction are they likely to get, in a race likely to focus largely on national issues, by accusing Kaine of having spent too much time on . . . national issues?

Against those supposed vulnerabilities, Kaine is quick-witted, upbeat and well liked, a formidable and energetic campaigner who’s never lost a bid for public office. In his last race, for governor in 2005, he ran an exceptionally shrewd and relatively gaffe-free campaign. And in 2012, he will very likely have the active support of Sen. Mark Warner, and of outgoing Sen. Jim Webb, who Kaine would succeed; both of them are Democrats and both are popular.

If there’s any Democratic primary challenge--Rep. Bobby Scott, a Congressman who represents Richmond and and part of Hampton Roads says he’s thinking about a run--Kaine, who’s highly popular within the Democratic party, will make quick work of it. Meanwhile, on the Republican side, George Allen, the former Virginia senator and governor, is likely to have his hands full fending off at least one serious challenger from the right, Jamie Radtke, who leads Virginia’s highly energized Tea Party. On her web site, she’s already poking holes in Allen’s conservative credentials by running a mocking feature called “This Week in George Allen History,” skewering him for his big-spending, earmark-loving, inside-the-Beltway record.

And let’s not even get started on Allen’s obliquely racist and “Macaca” past--this in a state whose minority population jumped from 30 percent to more than 35 percent over the last decade.

If Kaine and Virginia Democrats have anything to fear, it’s not the gloating-for-show they may hear from the GOP; the real peril is over-confidence in their own ranks.