The news that former Gov. Tom Vilsack will serve as President-elect Barack Obama’s Secretary of Agriculture has left political insiders with one fewer interesting hypothetical going into the 2010 campaign cycle.  Vilsack was seen as the Democrats’ strongest challenger to Sen. Chuck Grassley, a seemingly unbeatable Republican incumbent.

Though Vilsack’s appointment does not completely preclude a bid for the U.S. Senate, it probably precludes one in 2010.  A campaign against Grassley would have to start early — likely within the next six months — and the President-elect probably got an assurance from Vilsack that he would not skip out on his new job so soon.

A lot of Democratic insiders seem to think that Vilsack was their party’s only hope against Grassley in 2010.  They might be right, but that is no reason to offer an unconditional surrender.

The U.S. Senate race will be at the very top of the ballot in two years, and Democrats should have learned the lesson of 2004 by now: Running a laughable candidate against Grassley can cost you the “straight ticket” votes you need in other races.  If Art Small had lost to Grassley by only 300,000 votes instead of the nearly 600,000 votes he lost by that year, don’t you think Sen. John Kerry could have gotten the paltry 10,000 votes he needed to win statewide?

Gov. Chet Culver could face a tough race for reelection in 2010.  He could do without the added weight of another landslide victory for Grassley holding him down.

So let’s take a look at the Democratic bench.

Most of the big name Democrats in Iowa politics are likely to sit this race out, unwilling to launch a losing battle against such a behemoth.  But there are a few possible candidates who would see little political downside to running a respectable-but-unsuccessful campaign to unseat Iowa’s senior senator.  (As far as I know, none of the individuals listed below has expressed an interest in running, but each could conceivably lose to Grassley by less than 10 percentage points.)

Christie Vilsack, wife of the incoming Secretary of Agriculture, has indicated that she will continue some of her work in Iowa when her husband starts his new job in Washington, D.C.  She has always been at least as popular statewide as her husband, and, after years of appearing and raising money on behalf of Democrats and liberal organizations across Iowa, she has a thick Rolodex of favors to call in.

Iowa Senate Majority Leader Mike Gronstal might have bigger hopes for his political future, but if he is content with his seat in the State Senate, he could run against Grassley without giving it up, since his term lasts until 2012.  Because he represents a district in Western Iowa, he should have better name recognition there than most Democratic candidates.  And because of his work for the Democratic Legislative Campaign Committee, he has a national fundraising network to tap.

Former Congressman and Economic Development Director Mike Blouin, who was Tom Vilsack’s unenthusiastically anointed pick to replace him in 2006, is keeping a relatively low profile these days.  But if the 2010 election is about the economy, he might have enough expertise and political acumen to hold Grassley to a tight race.  His 2006 runningmate, Dr. Andrea McGuire, might also be an interesting case if she can survive the 2010 Democratic primary.

Liberal gadfly and former State Rep. Ed Fallon, who has lost two high-profile Democratic primaries over the past four years, would be an interesting choice to run against Grassley.  Fallon has fairly strong statewide name recognition, and if he played along with the Democratic establishment enough to communicate a coherent message on behalf of his party’s whole ticket, he could lose by less than 10.

State Sen. Jeff Danielson had a political near-death experience in this year’s election, but he could still be a formidable candidate.  His biography is pitch-perfect (think “Navy,” and then think “firefighter”).  Under the right conditions, he could put together a coalition that would swamp his opponents out of the Democratic primary.  And he probably would not embarrass himself in the limelight.

There are also a few lesser-known state senators who have the ambition and energy needed to run statewide.  Tom Rielly, a moderate from conservative-leaning Oskaloosa, might be the strongest general election candidate among them.  A race like this would lay the groundwork for higher ambitions down the road.

Any names I missed?