Manchin recently made national headlines with his attempt to increase background checks for gun purchases, a move that had some Republican support.
"At least they're talking to each other," Casey said. "They still don't agree, but a new spirit of at least conversation has begun. I believe I can bring that same spirit to the United States Congress on the House side."
Others in attendance Tuesday included former Sen. Carte Goodwin, former National Guard Adj. Gen. Allen Tackett, state AFL-CIO President Kenneth Perdue and Charleston Mayor Danny Jones.
Jones said he thinks Casey is a class act who would be in touch with reality. A Republican, Jones said he openly supported Tomblin, too.
"I'm an independent person, and if I want to get involved in Nick's campaign, I may," Jones said, adding Casey asked him to attend Tuesday.
"I made sure, 'Are you sure?' because I carry a little baggage," Jones continued. "But he's a great person, a really high-class guy."
Kanawha County Commission President Kent Carper called the Daily Mail to say he is endorsing Casey. He said he couldn't imagine supporting anyone else in the race.
In a brief speech, Casey outlined several areas of focus for his campaign. Improving public infrastructure is his top priority. He said it would allow for business growth and job creation, his second priority.
Implementing a unified energy policy was his third priority: he said it was "embarrassing" for the United States to use so much foreign oil, and he decried the federal Environmental Protection Agency for overreach regarding coal.
He specifically mentioned veterans and seniors in his speech, providing few details other than to say they were important issues to him.
Casey said the timing for his announcement wasn't an attempt to "freeze out other candidates," but was because he has started receiving money. He didn't know offhand how much money his campaign had received. He's still working on getting his campaign staff together.
Delegate Doug Skaff, D-Kanawha, recently said he was weighing a run for Congress. In a phone interview Tuesday, Skaff said he knew Casey was going to run and it wouldn't affect Skaff's own decision. He still plans to announce his decision sometime in May.
Considering Casey's involvement in the state over the years -- he helped Manchin on several campaigns -- Skaff said it wasn't a surprise to see so many people attend Tuesday's announcement.
"Just because they were there doesn't mean that's an endorsement," Skaff added.
Rod Snyder, president of Young Democrats of America and son of state Sen. Herb Snyder, D-Jefferson, said he also is considering a run for Congress.
Republicans believed to be interested in the seat include House Minority Leader Tim Armstead, R-Kanawha; Senate Minority Leader Mike Hall, R-Putnam; Delegate Patrick Lane, R-Kanawha; Delegate Eric Nelson, R-Kanawha; former lawmaker Steve Harrison and former state GOP chairman Mike Stuart.
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