This is arguably the most volatile period for the House battleground map, as partisan operatives are making their final ad spending decisions and beginning to move money away from some races to put more resources into other contests.

The Senate map is much less fluid, yet this is the time when some races begin to fade in terms of their competitiveness and others become more so. In recent weeks we’ve seen the New Mexico Senate contest move to the less competitive category, while Connecticut and Indiana are now fully in play. We are still monitoring developments in Connecticut (and could make another ratings change there soon), but new polling in Indiana confirmed for us that a ratings change was due.

We are making the following ratings changes today:

• Indiana Senate: Leans Republican to Tossup
  After months of Democratic polls showed a tied race, a new bipartisan poll from Howey Indiana Politics showed Rep. Joe Donnelly (D) leading state Treasurer Richard Mourdock (R) by 2 points. And that’s after conservative groups started dropping six-figure weekly ad buys in the state. Game on.

• California’s 16th district: Likely Democratic to Safe Democratic
  A competitive race simply never developed here in the Central Valley against Rep. Jim Costa (D).

• California’s 21st district: Likely Republican to Safe Republican
  This is a district that at one time in the cycle had the potential to be among the state’s most competitive. But a series of solid Democratic recruits opted out of running against state Assemblyman David Valadao (R), and the Democrat who emerged from the top-two primary has been underwhelming.

• Illinois’ 8th district: Likely Democratic to Leans Democratic
  Once a political goner, Rep. Joe Walsh’s (R) re-election bid is showing signs of life thanks to six-figure buys from a super PAC and the National Republican Congressional Committee. Still, Iraq War veteran Tammy Duckworth (D) is favored to win this Democratic district.

• Iowa’s 3rd district: Leans Republican to Tossup
  A few months ago, Rep. Tom Latham (R) seemed to have a decisive edge in this race over his colleague, Rep. Leonard Boswell (D). But a competitive presidential race, plus outside help for Boswell, has made this race more competitive — despite Latham’s incredible cash advantage.

• Michigan’s 3rd district: Leans Republican to Likely Republican
  National parties have yet to even reserve airtime here, which means it’s not on their radar. The 1st district remains the only competitive House race in Michigan.

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  Michigan’s 11th district: Leans Republican to Likely Republican
  After one of the oddest primaries in recent memory, reindeer rancher Kerry Bentivolio (R) is coasting through the general election against internist Syed Taj (D) in this Republican district.

• North Carolina’s 8th district: Leans Republican to Likely Republican
  Rep. Larry Kissell (D) has always had a difficult path to re-election in a more Republican district (thanks to redistricting). But with recent news that the Democratic Congressional Campaign Committee canceled two weeks of airtime, the window for Kissell to beat Republican nominee Richard Hudson grew a good bit narrower. Republicans have been on the air for weeks pounding Kissell, without any cover from his national Democratic allies.