Mr. Rubio has raised $30.2 million since 2009, with $3.2 million cash on hand. Mr. Cruz has raised $18.1 million, with $1.4 million on hand. Mr. Ryan raised $8.8 million this cycle, with $2.9 million on hand. All three can transfer these balances to a presidential campaign. Mr. Paul has raised $13.6 million since 2009, with $2.9 million on hand—but he’s simultaneously running for re-election in 2016 and not likely to transfer his cash.

Seven candidates formed federal PACs, mostly to broaden donor bases. Only Mr. Rubio ($3.7 million) and Mr. Ryan ($3.2 million) raised more than $2 million.

Dr. Carson may have the most impressive list of new small donors. The Draft Carson Committee (with which he legally could not be involved) used his name to raise $11.1 million, spent $10.2 million (92%) on overhead and devoted $531,788 (5%) to supporting midterm candidates. American Legacy PAC (Dr. Carson heads its anti-ObamaCare project) used his signature to help raise $6.5 million, and spent $5.9 million (91%) on overhead and gave $140,090 (2%) to candidates. If Dr. Carson runs, his campaign presumably can use those donor names.