I used to say that if you put a gun to my head and demanded to know who’d be the 2008 Republican presidential nominee, my answer would be: “Shoot.”

[IMGCAP(1)]Now, I’m almost ready to say the same about the Democratic nominee and the next president, too.

I still think the likeliest answer to the last two questions is Sen. Hillary Rodham Clinton (D-N.Y.), but that’s a lot less certain than it used to be.

Meantime, the Republican race is boiling down to two major contestants, former New York Mayor Rudy Giuliani and ex-Massachusetts Gov. Mitt Romney, but who’s going to win is still unknowable.

Polling continues to show that Americans favor a generic Democratic candidate as their next president and that only Giuliani or Sen. John McCain (R-Ariz.) has much of a chance against top Democrats.

But once the nominees are known, the clock will be reset and the race will tighten. The Democrat might be favored, but issues of executive experience and foreign policy could make it a contest.

In the race for the Democratic nomination, if Clinton wins the Iowa caucuses on Jan. 3, she’s almost certain to be the nominee.

But now you can easily see her losing in Iowa. And if she finishes third or significantly trails as No. 2 — especially behind Sen. Barack Obama (Ill.) — it could set off a cascade that causes her to lose New Hampshire and then the nomination.

Polls suggest that Clinton has built up lots of firewalls in states after New Hampshire, where she currently leads by 13 points. She leads in Michigan (Jan. 15) and Nevada (Jan. 19) by more than 20 points, according to RealClearPolitics.com averages, South Carolina (Jan. 26) by 14 points and Florida (Jan. 29) by 26 points.

And in Feb. 5 states like California, New Jersey and Pennsylvania, her leads are close to 30 points.

Yet, defeats in Iowa and New Hampshire could burn through the firewalls and re-create the dynamic of 1984, where the establishment candidate, former Vice President Walter Mondale, almost lost the nomination to fresh-face challenger Sen. Gary Hart (Colo.).

Mondale pulled it out only because his staff succeeded in convincing the media that Georgia and Alabama were the key contests on Super Tuesday. Mondale won them, though Hart won bigger states like Florida, Massachusetts and Washington, and even bigger primaries later in Ohio and California.

To the extent that polling is reliable in a caucus state like Iowa, indications are that Clinton is in deep trouble. The topline ABC/Washington Post poll results showing Obama with 30 percent, Clinton with 26 percent and former Sen. John Edwards (N.C.) with 22 mean less than other factors.

Specifically, the polls indicate that second-tier candidates like New Mexico Gov. Bill Richardson, Sens. Joe Biden (Del.) and Chris Dodd (Conn.) and Rep. Dennis Kucinich (Ohio) split up 25 percent of the vote among them.

The way the Iowa caucuses work, after a first round of balloting, candidates receiving less than 15 percent support get dropped on subsequent ballots, putting a premium on being the second choice of caucus-goers.

In early November, the CBS/New York Times poll indicated that Edwards was the second choice of 30 percent of supporters of second-tier candidates, while Obama was favored by 27 percent and Clinton by just 14 percent.

The ABC/Washington Post poll indicated that among Iowa Democrats, Clinton’s points of advantage — “strength and experience” — are far less important than Obama’s “new direction and new ideas” by a margin of more than 20 percent.

If caucus-goers between now and January decide that they need to support the candidate best able to win the presidency in November and best qualified to govern, they’ll pick Clinton, much as they dropped Howard Dean for Sen. John Kerry (Mass.) in 2004.

If they primarily want someone who says what he thinks and understands the problems of people in Iowa, it will be Edwards. If they opt for trying to change Washington, it will be Obama — according to current polls.

It’s hard to see how Edwards goes on to win the nomination even if he wins in Iowa. He’s running a distant third in New Hampshire and everywhere else. But then, Hart didn’t even win Iowa in 1984 — he got 17 percent to Mondale’s 49 percent — and almost caught the frontrunner.

Obama is more likely to defeat Clinton for the nomination — especially if an Iowa victory makes him the top story of the night and excites Independents in New Hampshire to vote in the Democratic primary.

More than 40 percent of registered voters in the state are Independents eligible to vote in either party’s primary. A poll this summer indicated that nearly 70 percent of them might vote in the Democratic primary.

Clinton currently leads Obama in New Hampshire, 36 percent to 23 percent, according to RealClearPolitics averages. But an Obama victory in Iowa could change that.

On the Republican side, Romney is losing his early Iowa advantage to former Arkansas Gov. Mike Huckabee. If Romney doesn’t win Iowa, it’s a blow to his strategy of collecting a run of early victories that would propel him past Giuliani, the national and late-state frontrunner.

Romney still has a significant lead in New Hampshire — 33 percent to 18 percent for Giuliani and 16 percent for McCain — but Giuliani is challenging.

And Giuliani also is catching up to Romney in Michigan, is ahead in Nevada and tied in South Carolina. In Florida, Giuliani leads by 17 points and in Feb. 5 states like California and New Jersey, by nearly 30 points.

It’s hard to see how Huckabee could capitalize on an Iowa victory, though he might attract some Independents in New Hampshire, or how McCain could convert a New Hampshire victory to capture the nomination. Former Sen. Fred Thompson (Tenn.) seems to be catching fire nowhere.

In the latest Gallup polls for the general election, Clinton is leading Giuliani by just five points, McCain by six and Romney by 16. Obama is tied with Giuliani, leads McCain by just three and beats Romney by 17.

In other words, if Giuliani (or McCain) wins the GOP nomination, the general election outcome could be very close, with the GOP challenging the Democrat on national security, taxes and the size of government.

Romney, by the time he won the nomination, would close the present gap and challenge on the basis of executive experience as well as issues.

So, bottom line, Clinton still has an edge, but it’s nothing to bet much money on. If you’re inclined to do so, though, Ladbrokes of London puts the odds on Clinton at 1-2, Giuliani at 7-2, Romney at 11-2, Obama at 8-1 and Edwards at 25-1.