( CNN ) -- A day after four of Sen. John McCain 's top political strategists stepped down , the co-chairman of his Florida campaign was arrested Wednesday for allegedly offering an undercover police officer money for a sex act , Titusville police said . Florida state Rep. Bob Allen faces charges of solicitation for prostitution after he was arrested in a Titusville city park that had been under surveillance , police said . He allegedly offered an undercover police officer $ 20 for the unspecified act . His attorney , Philip Lupo of Titusville , said the charge was a second-degree misdemeanor . Allen told CNN affiliate WFTV the incident was `` a very big misunderstanding . '' `` This is a very gross mistake , a very big mistake , '' he said , adding that this is what the judicial system is for . Allen said he helped build the park , and was there looking around . At a late-afternoon press conference Thursday , Allen made a statement but took no questions . `` I am filing a not guilty plea . I am vigorously going to fight this , '' he said . `` I am not resigning my office , because the people elected me [ and ] want me to do a good job and I am going to do a good job for them in finishing this term . ... `` This is an ugly and unpleasant situation that has been thrust upon me and my family that is not true , it is inaccurate and it is therefore not guilty . '' There was no initial comment from the McCain campaign . In March , the McCain campaign issued a news release on its Florida leadership team , saying , `` Allen will serve as a House co-chair for Sen. McCain 's campaign . '' Allen was elected to the Florida House in 2000 . His arrest comes a day after McCain 's campaign manager , Terry Nelson , and chief strategist , John Weaver , announced their departures in joint statements released by the campaign . McCain 's deputy campaign manager and political director also resigned this week . Earlier this week , U.S. Sen. David Vitter , the Southern regional chairman for Rudy Giuliani 's presidential campaign , was linked to the so-called D.C. Madam 's escort service . Vitter , a Louisiana Republican , said , `` This was a very serious sin in my past for which I am , of course , completely responsible . Several years ago , I asked for and received forgiveness from God and from my wife in confession and marriage counseling . '' It was the second blow for Giuliani 's campaign . Last month , South Carolina Treasurer Thomas Ravenel , the state chairman for Giuliani 's campaign , was indicted on federal cocaine charges . E-mail to a friend . CNN 's Steve Brusk contributed to this report .
McCain campaign co - chairman allegedly offered undercover cop $ 20 for sex . State Senator Bob Allen says he is innocent , did not resign from campaign . He says he was merely looking around park he helped build . Several top strategists resigned from McCain campaign a week earlier .