The retirement wave continues in the US Senate, although this one hardly surprises. Sen. John Ensign, who has been battered by an adultery and then a political payoff scandal, will hold a news conference today in Las Vegas to discuss his political future, and the indications are that he will retire.

Sen. John Ensign is expected to announce at an afternoon news conference in Las Vegas that he will retire rather than face a brutal 2012 re-election campaign, according to knowledgeable sources.

The Nevada Republican, who has been embattled since revealing he had an affair with the wife of a former aide, was facing a possible primary challenge from Rep. Dean Heller (R). Heller is now expected to run for the open Senate seat.

This resembles the Chris Dodd retirement in some ways. Dodd was toast in 2010, and Richard Blumenthal seen as a much better bet for the Democrats. That’s exactly how it ended up working out. Similarly, Heller has been much stronger in the polling than Ensign, who is obviously scarred by his affair with Cindy Hampton, the wife of his deputy chief of staff, as well as having his parents pay the Hampton’s $96,000 in hush money, and him helping Doug Hampton find a lobbying job. While David Vitter inexplicably made it through an election in Louisiana while tainted by a sex scandal, Nevada is a different place, and the inclusion of hush money and potential Senate ethics violations made this a very difficult climb for Ensign.

Heller now enters the race as the prohibitive favorite, though there are possibles on the Democratic side. The DSCC has been scouting possible candidates, including Attorney General Catherine Cortez Masto, Treasurer Kate Marshall and Secretary of State Ross Miller. Given what happened last cycle, when Harry Reid was basically the most unlikable person in Nevada and still won re-election, thanks to a great ground campaign and a terrible opponent in Sharron Angle, it would be foolish for Democrats not to compete in Nevada. But Heller will be tougher to beat than Ensign.

I want to remark again on how remarkable it is that just three months into the 2012 campaign cycle, 8 of the 33 Senators up for re-election will be retiring. Since 2006, there are 42 new Senators in the upper house, and with these 8 retirements, that means that at least half of the body will be made up of people who haven’t been there longer than 7 years, come 2013. This is a very newer, younger Senate, and despite the setback in rules reform this year, I think that bodes well for some changes down the road.

UPDATE: Another reason why it makes sense for Democrats to get a good candidate for this race is that you never know who Nevada’s electorate will select in a primary. Angle may run again, and for all the buyer’s remorse after her epic loss, she or someone just as extreme may come out of that primary.