After college, he was invited to the Dallas Cowboys' training camp; he gave up football when told he would have to convert from linebacker to offensive lineman.

He returned to Cincinnati to run for the first district seat in the United States House of Representatives which was being vacated by Tom Luken.

Following his close defeat, Blackwell was appointed by President Bush as US ambassador to the United Nations Commission on Human Rights.

George Voinovich appointed Blackwell as Ohio State Treasurer to complete the term of Mary Ellen Withrow.

[10] Prior to the 2004 presidential election, Blackwell had announced he would enforce an Ohio State election law decreeing that any person who appeared at a polling place to vote but whose registration could not be confirmed would be given only a provisional ballot; if it were later determined that the person had attempted to vote in the wrong precinct, then their provisional ballot would not be counted.

The Democratic party filed a lawsuit claiming that the policy was "intended to disenfranchise minority voters" and in violation of federal election law, specifically section 302 of the Help America Vote Act (HAVA).

(pdf) On December 27, 2004, Blackwell requested a court order to protect him from being interviewed in the Moss v. Bush case, a challenge of the presidential vote.

In many cases these irregularities were caused by intentional misconduct and illegal behavior, much of it involving Secretary of State Kenneth J. Blackwell, the co-chair of the Bush-Cheney campaign in Ohio.

[14][15]On March 1, 2006, Blackwell's office accidentally published a list of 1.2 million Social Security numbers of Ohio citizens on a website along with their business filings.

A Federal class-action lawsuit was filed by Darrell Estep, who claimed that the release of the data had resulted in his Social Security number appearing three times on the public website.

[16] The lawsuit was settled on March 28, 2006, after the numbers were removed from the website, a registration process was enacted to view the data, and Blackwell's office agreed to make monthly progress reports to the court.

Blackwell stated that he considered the issue to be closed, but Petro disagreed, saying that he would use "maximum due diligence" to ensure that the data was not copied before it was returned.

[23] He attributed the purchase to an unidentified financial manager at Credit Suisse First Boston who he said had, without his knowledge, violated his instructions to avoid potential conflict of interest.

[24] When Cuyahoga County's primary was held on May 2, 2006, officials ordered the hand-counting of more than 18,000 paper ballots after Diebold's new optical scan machines produced inconsistent tabulations.

Blackwell's opponents in the general election were Democratic Congressman Ted Strickland, Libertarian professor emeritus Bill Peirce, and Green Bob Fitrakis.

[26] Blackwell faced an uphill battle; according to a broad survey reported by The Plain Dealer on April 30, 2006, Ohio voters would "prefer to see a Democrat occupy the governor's mansion.

In his 2002 campaign for re-election to the post of Secretary of State, Blackwell took the position that he would favor abortions in the case where the life of the mother was at stake.

[34] Blackwell was criticized by Petro, for declining to engage in three planned debates which had been organized by the Dayton Daily News and the City Club of Cleveland.

According to The Columbus Dispatch, "Blackwell said he has 'shared plenty of forums' with Petro and that he wants to focus on talking to Republicans in the final days of the campaign.

[38] On April 16, 2006, the Toledo Blade reported that Blackwell had accepted more than $1 million in campaign contributions from "employees of firms seeking business with the statewide offices he's held over the past 12 years."

The investigators argue that the suggestion of quid pro quo based on the actions of contributors raise an issue of a serious conflict of interest.

"[39] After winning their respective primaries, both Blackwell and his Democratic opponent were able to raise record sums, in part because of the national attention paid to the race.

The pastors accused the two organizations of sponsoring at least nine events with Blackwell as the sole invited politician, described as "partisan voter-registration drives," and of distributing biased voting guides.

Russell Johnson, pastor of the Fairfield Christian Church in Lancaster, Ohio, defended his actions by saying that the event in question was not a "meet the candidate forum," but rather that he was giving Blackwell "an award for courageous leadership.

Rod Parsley, pastor of World Harvest church, have argued that the investigation was politically motivated and violated their constitutional right to free speech.

Mark Everson, commissioner of the IRS responded, "you don't have an automatic or constitutional right to a tax exemption, and that's where the line has been drawn.

"I unequivocally support the Second Amendment right of every law-abiding Ohioan to keep and own firearms for hunting, personal protection and any other lawful purpose," said Blackwell.

He won early endorsement from the state chairmen in Louisiana (Roger F. Villere, Jr.), Texas (Tina Benkiser), and Oklahoma (Gary Jones).

In October 2011, the National Federation of Republican Assemblies elected Blackwell their Executive Vice President at their Des Moines, Iowa Presidential Preference Convention.

During the presidential transition of Donald Trump, Blackwell led appointment selections for positions involving domestic issues.