Does this mean war between Ensign and Reid?

(Steve Sebelius/Slash Politics) – Many times since 1998, pundits have speculated about the end of the infamous Harry Reid-John Ensign non-aggression pact. Forged in the tough, 428-vote contest between the two men 12 years ago, the pact has been the bane of partisans on both sides of the aisle who’d love to see their home state senators mix it up.

Has that time come?

Although Reid and Ensign have offered tepid support to each other’s challengers over the years (Republican Richard Ziser in 2004, Democrat Jack Carter in 2006) neither man has really gone all in to help defeat the other. But this time around, Ensign put his back into taking out Reid on behalf of Republican challenger Sharron Angle.

Ensign persuaded a reluctant former Congresswoman Barbara Vucanovich to endorse Angle, even after Vucanovich denounced Angle as “very rigid” and “a very difficult person.” While persuading Vucanovich, Ensign reportedly told the retired congresswoman, “we need to defeat Harry Reid.”

In addition, Ensign lent his stentorian voice to an Angle phone bank.

And, Ensign showed up to play his good friend Reid during Angle’s debate prep, according to a blog by my colleague Jon Ralston.

The point? Ensign campaigned more aggressively for Angle than either he or Reid has ever campaigned for a challenger since striking their pact after the 1998 election. And that cannot have gone unnoticed by Reid.

Don’t forget, Ensign is hobbled by the scandal of his affair, the official investigations of whether he broke Senate ethics rules or even criminal laws by paying his mistress’s family and helping her husband find lobbying work in possible violation of cooling-off laws. He’s been unable to raise much money (for his campaign accounts or a legal-defense fund). And he’s on the ballot in less than two years.

In other words, he’s got a very difficult, very narrow path to victory as it is, and he doesn’t need Reid as an enemy.

So why do it? The obvious answer is that Ensign surveyed the field, concluded Reid was finished and decided to go all-out for Angle in order to bolster his own chances of staying in the Senate despite the recent unpleasantness. Like many Nevadans, Ensign wrote Reid off. And like many Nevadans, he was wrong.

Only this isn’t just a “my bad” moment. Ensign may very well have crossed the line on the longstanding pact with Reid. The relationship between the two bears close scrutiny, since change seems to be in the air. And that change cannot be good for Ensign.