Rick Santorum is a party crasher.

He has helped crash the Republican Party into a wall of public resentment. He suspended his campaign this week, but not before doing incalculable damage to the Republican brand and to the party’s presumptive nominee, Mitt Romney.

For months, Santorum became the favored face of the most conservative faction of the party, the one person who gave them a viable chance at resisting Romney.

Santorum surged by dragging the debate so far to the right he couldn’t see the middle with a telescope. The base dropped all pretense of moderation or even modernity and followed Santorum down a slippery path that led to a political abyss of social regression. The rest of America watched in stunned disbelief and was left to wonder: Was this the rise of some sort of “Judeo-Christian Shariah” movement, as the political comedian Dean Obeidallah pointed out on CNN.com?

David Maxwell/European Pressphoto Agency

Instead of small government and fiscal conservatism, Santorum overwhelmingly promoted — and the public overwhelmingly focused on — his apparent obsession with sex and religion.

He argued that allowing women to use contraception to control when they got pregnant — one of the foremost decisions a woman can make about her body, her health and her and her family’s economic security — was morally wrong.

Santorum opposed abortion even in cases of rape and incest, saying that women should be forced to carry those pregnancies to term and just accept the “horribly created … gift” and “make the best of a bad situation.”

Santorum not only adamantly opposed same-sex marriage, saying that he would support a constitutional amendment banning it, he went so far as to say that gay people who had legally married under the laws of their states would have their marriages rendered “invalid.”

But he didn’t stop there. Santorum expressed other outlandish, head-scratching views on many more issues that seemed to cement his position as a man out of step with a modern America.

He slammed the president’s promotion of self-improvement through higher education as snobbery although he himself has bachelor’s, master’s and law degrees.

He suggested that women might be too emotional to serve on combat missions:

I do have concerns about women in frontline combat. I think that can be a very compromising situation where — where people naturally may do things that may not be in the interests of the mission because of other types of emotions that are involved.

And of course he denies climate change, calling climate science “political science,” and remarking: “The dangers of carbon dioxide? Tell that to a plant, how dangerous carbon dioxide is.”

I could go on, but it’s all just too exhausting and depressing.

At the same time, Santorum continuously chipped away at Romney as a dishonest man and a weak conservative, as well as the worst candidate to run against President Obama.

The shift in the debate, which Santorum helped create, and his withering attacks on the front-runner forced Romney to move further right than was politically prudent.

As a result, Romney is now weaker than any post-primary party nominee in recent political history. According to an analysis of CNN polling data stretching back to 1996, compiled by Zeke Miller of BuzzFeed, Romney is the only presidential nominee to emerge from the primaries with a net negative favorability rating.

A Washington Post/ABC News poll last week also painted a troublesome portrait for Romney this fall. In a head-to-head matchup, Obama beat Romney by seven points. But some of the trends among specific constituencies were even more troubling. As the Post pointed out:

If a Romney-Obama matchup were held today, registered voters would divide 51 percent for the president to 44 percent for the former Massachusetts governor. That is similar to the edge Obama held in a Post-ABC poll in February; the two were more evenly matched in March. A wide gender gap underlies the current state of the race. Romney is up eight percentage points among male voters but trails by 19 among women.

Furthermore, the newspaper noted:

In addition to his big lead among women — Obama won that demographic by 13 points in 2008 — the president is moving to secure other key elements of his winning coalition. As he did four years ago, he has overwhelming support from African-Americans — 90 percent back his re-election effort — and he has a big lead among those ages 18 to 29.

Santorum has left a wake of destruction for Romney and the Republicans that many Americans won’t soon forget. As we turn to the general election, if Romney can’t count on electoral excitement, he must hope for electoral amnesia — and he has Santorum to thank for much of that.

(Exit Santorum, stage far, far right.)