WASHINGTON (Map, News) - If Republicans continue tomorrow on their self-destructive path and cement John McCain’s status as front-runner, they may well be ensuring victory for Democrats in this fall’s presidential election.

Barack Obama is going to be on the Democratic ticket one way or the other: If Hillary Clinton wins the nomination, she will have to select him as her running mate. He has personal appeal that she lacks so profoundly; he represents change that the voters say they want.

Without him, she is just an unlikable retread running on a return to the past. Moreover, after her husband’s artless race baiting before the South Carolina primary, rejecting Obama would be viewed as a racial snub and jeopardize her support among black voters.

But if Obama is the nominee, he does not have to pick her; indeed, he would be wise to select someone else. Choosing Hillary would blunt his message of change and would only saddle him with her baggage — in particular, her husband. The prospect of Bill Clinton trolling the White House again is beyond distasteful.

And while some of Hillary’s supporters actually relish another two-for-one Clinton administration, it could hardly appeal to Obama to have the didactic duo as vice presidents. Dick Cheney is at least discreet in his manipulation of the Bush White House. The Clintons are constitutionally incapable of eschewing center stage.

But regardless of whether he’s on the top or bottom of the ticket, Obama’s presence makes McCain the worst candidate Republicans could choose. Obama’s youth implicitly focuses more attention on McCain’s advanced age. Obama has the Kennedy charisma and the Reagan charm. McCain is arrogant and famously ill-tempered. It is a mistake to underestimate the role likability plays in American politics.

McCain owes his success to left-leaning independents who vote for him in the primaries, but those are the people among whom Obama is rapidly gaining support. To have any chance of winning over conservatives, McCain will have to tack right, driving even more voters who supported him in the primaries into the Obama or Clinton camp.

And McCain is not going to win over conservatives. They despise him — and rightly so. McCain is a consistent supporter of high taxes, expansive government and more limitations on individual freedom. He voted against the tax cuts of 2001 and 2003. His most significant legislative achievement was so-called campaign finance reform regulating political advertising, which critics view as an unconstitutional restriction on free speech.

With Ted Kennedy, McCain co-sponsored a bill that would give citizenship to individuals in this country illegally — i.e., inflict on Americans millions of people who have no regard for the rule of law. (Shouldn’t any conservative — indeed, any sentient person — realize that when he finds himself agreeing with Ted Kennedy he should rethink his position?)

McCain is an ardent supporter of REAL ID, the law mandating a national identity card with a scannable bar code that will allow the government to track citizens’ movements. Functioning as an internal passport, the card will have to be presented before entering a public building, opening a bank account, boarding an airplane — even visiting a national park.

And don’t forget that McCain sponsored the legislation creating the Transportation Security Administration, which Americans now say they detest as much as the Internal Revenue Service.

The real problem is that if McCain is the Republican candidate, voters will have no real choice. Those who support America’s presence in Iraq may favor McCain’s stay-the-course position, but Clinton’s proposal for phased redeployment indicates that she would not act rashly.

Regardless of whether the winner is McCain, Clinton or Obama, a conservative will not be elected. Given their inevitable disappointment, many Republicans may not vote at all. Others may vote for Clinton or Obama, merely to spite McCain.

Republican hopes for holding on to the White House were based on a two-part scenario: that Hillary Clinton would be her party’s nominee, energizing the anyone-but-Hillary base. A different Republican candidate could have capitalized on that; McCain has deflated it already. Instead, he has tapped an even stronger conservative sentiment: anyone but McCain.

Examiner Columnist Melanie Scarborough lives in Alexandria.