ATLANTA (Reuters) - The costliest U.S. congressional race in history will be decided on Tuesday in suburban Atlanta, where America’s divisive political climate has been on display in an election seen by some analysts as a political test for President Donald Trump.

Days after a lone gunman opened fire on U.S. lawmakers at a baseball team practice in Virginia, a conservative group was running a TV ad in Atlanta that, with no evidence, appears to link the Democratic candidate, Jon Ossoff, to the shooting spree.

Ossoff called the ad “shameful” in a statement. The Atlanta Journal-Constitution newspaper reported that Ossoff’s Republican opponent, Karen Handel, also condemned the ad.

It was an ugly, last-minute twist in the Ossoff-Handel contest for the U.S. House of Representatives seat vacated by Tom Price, who resigned after becoming Trump’s secretary of the Health and Human Services Department.

Total spending in the Georgia race for all candidates has topped $56 million, including tens of millions by outside groups, according to the Center for Responsive Politics, a campaign finance watchdog in Washington, D.C., easily topping the previous record of $29.5 million set in a 2012 Florida race.

Out of the total, $51.9 million has been spent on Handel and Ossoff, the Center for Responsive Politics said.

Envelopes containing a white powder turned up last week in the home mailboxes of Handel and a few neighbors, prompting a probe by the Federal Bureau of Investigation. The Washington Post reported that the powder was only baking soda and both candidates now are traveling with bodyguards.

Slideshow ( 8 images )

The district spans affluent and increasingly diverse suburbs north of Atlanta. It has elected Republicans for decades, but Trump carried it by only 1 percentage point in 2016.

Ossoff, 30, initially drew national attention with the slogan “Make Trump Furious,” inspiring volunteers from as far away as Oregon to knock on doors and make phone calls for him.

Handel, a 55-year-old former Georgia secretary of state, has painted Ossoff as an inexperienced tool of national liberal interests who does not live in the district he hopes to represent. Like Ossoff, Handel rarely mentions Trump.

Whatever the outcome, the race will not significantly alter the balance of power in Washington, where Republicans control the House by a wide margin. But victory could provide a blueprint for Democrats on how to win outside of their urban, coastal strongholds.

Democrats fell short in special House elections earlier this year in Kansas and Montana, in districts that Trump won by double-digits. Also on Tuesday is a race in South Carolina, which Republicans are expected to win handily, for a replacement for Republican Mick Mulvaney, now Trump’s budget director.