Pennsylvania’s Republican U.S. Senator Pat Toomey is not seeking reelection and a wide field of candidates want to fill that seat. Already, candidates are spending campaign money on billboards, radio, and television advertising and that is going to intensify. Most will spend well over $174,000, the annual salary of a U.S. senator. These months, now until the May 17 Pennsylvania primary, are a short window for candidates to introduce themselves to the public, lay out their platforms, and convince their party to put them on the ballot for the Nov. 8 general election. At least 18 candidates are running for Pennsylvania’s open U.S. Senate seat. At one point there were at least 30, but some have dropped out, and others have little or no internet presence or budget. Here is a look at the 18, organized by party affiliation and then by the amount of campaign money raised, according to …