The Cook Political Report, a nonpartisan election analysis organization, has shifted its rating of the next major House special election to a toss-up — another sign that Democrats could make the red-seat race competitive.

Cook shifted the rating of Ohio's 12th Congressional District, vacated after former GOP Rep. Patrick Tiberi's resignation earlier this year, from a "lean Republican" seat to a "toss up."

The move comes just weeks before the May 8 primary, where voters will cast their ballots in the special election primary as well as the general election primary. Voters need to choose someone to fill Tiberi's term through 2018, as well as their next member for the Congress that starts in 2019.

Crowded fields on both sides of the aisle complicate the handicapping in the race, as it's possible that the winner of each primary will emerge with a relatively low share of the vote.

On the GOP side, state Sen. Troy Balderson has the backing of Tiberi and the Republican Main Street Partnership. Both have dropped six-figure advertising buys on Balderson's behalf.

Delaware County Prosecutor Carol O’Brien has the backing of state Auditor Dave Yost, while state Sen. Kevin Bacon has been endorsed by the Franklin County GOP.

Tim Kane, a veteran who has worked at Stanford University's Hoover Institution and the conservative Heritage Foundation, has the support of former Secretary of State George Schultz.