JOHNSTON — Beto O’Rourke acknowledged Thursday that his campaign needs a top three finish in Iowa to be viable in the race to the 2020 Democratic presidential nomination.O’Rourke, who was polling at less than 1 percent in a Monmouth University poll of likely Iowa caucusgoers earlier this month, is counting on a campaign reset focusing on gun violence and what he calls President Donald Trump’s racism to improve his likelihood of winning one of the proverbial three tickets out of the Feb.