The sense that the midterms could bring a realignment to both chambers of Congress continues to grow.  Both CQ Politics and the Washington Post’s Chris Cillizza see more Senate races moving into competitive positions, and almost all of them at the expense of Democrats.  Even the one race that Cillizza sees as potential good news for Democrats is based on a poll that has serious flaws in its methodology.

First, the more conservative take from CQ:

It’s hit that point in the election cycle where the competitive nature of Congressional races are shifting rapidly. Unfortunately for Democrats, the overwhelming majority of those shifts are in favor of Republicans.

The latest Senate race rating changes by CQ Politics includes five changes — in California, Washington, Wisconsin, Georgia and Iowa — that benefit Republican candidates. And Democrats can’t even catch a break on the sixth change, which moves Florida’s Senate race from Leans Republican to the more competitive Tossup category based solely of the strength of the Independent campaign run by Gov. Charlie Crist .

CQ adds Wisconsin, Washington, and California to its list of contested races, all of which are bad news for Democrats.  In all three, CQ notes, the Democratic incumbent was not thought vulnerable even in a bad year for Democrats.  The only one still leading in the polls is Barbara Boxer, who still can’t get close to 50%, and Fiorina has gotten within the margin of error in most surveys and even led in one.  CQ also moves Iowa and Georgia out of the competitive categories, saying that Chuck Grassley and Johnny Isaakson appear secure in their re-election bids — and even if they were vulnerable, Democrats won’t have the money to go on the offense.

Cillizza sees 15 Senate seats at risk of flipping in November:

The simple truth is that over the past six to nine months, the Senate playing field has expanded to the point where there are now (at least) 15 races where a party switch is a real possibility — if not a probability.

Most of that expansion has benefited Republicans, who have effectively taken advantage of a national playing field tilted in their favor to take previously non-competitive races like Washington and Wisconsin and put them on the target list.

Democrats have a few more opportunities as well — most notably in Kentucky where ophthalmologist Rand Paul‘s (R) uneven campaign has created an opening for state Attorney General Jack Conway. (An independent poll released Thursday showed the two in a statistical dead heat.)

The Kentucky race isn’t a slam-dunk for Republicans, but this poll isn’t a reliable indicator of the race, either.  Its weighted sample has a 16-point advantage for Democrats, 54.2% to 37.5% for Republicans and only 8.2% independents.  In 2008, in what most people would consider a banner year for Democrats, John McCain beat Barack Obama by a margin of 57/41 in Kentucky.  If it takes a 30-point swing in the sample to get Jack Conway into a statistical dead heat with Rand Paul, that tells us all we need to know about the “opportunity” Conway has in November.

On Cillizza’s list, only three other Republican seats appear: Florida, Ohio, and Missouri.  Florida won’t be won by a Democrat no matter what, and even if Crist wins it, he’ll caucus with whichever party takes power.  Ohio is winnable but close for Republicans, as is Missouri.  Both are traditionally red states, though, and with the economy tanking under Obama, Reid, and Pelosi, Democrats had better not expect to win either of them.  In both states, Republicans have experienced hands running for office, Rob Portman and Roy Blunt.  They’re not likely to make mistakes that will give their opponents an opening to exploit.

In order to take control, Republicans have to hold all of their seats and win most of the rest.  They have a good handle on the first five Cillizza lists: North Dakota, Arkansas, Indiana, Delaware, and Pennsylvania, plus some good news in Washington, Wisconsin, and Colorado of late.  It’s doable, but still long odds in winning control of the upper chamber.  Democrats, though, can’t rely on the odds and will have to start sinking their money into playing defense in these states.