INDIANAPOLIS (AP) — Evan Bayh was the Democrats’ prize Senate recruit this election cycle, a popular former senator and governor with a huge war chest and sky-high name ID.

Top Democrats heralded his surprise entrance into the race in July with hopes that Republicans would abandon his little-known and underfunded GOP rival, Rep. Todd Young, and give up on Indiana.

Instead, outside GOP groups including the Chamber of Commerce and the billionaire Koch Brothers have poured some $10 million into the race, essentially erasing Bayh’s fund-raising advantage and closing his lead over Young to low- or mid-single digits. With Republicans determined to retain their narrow majority in the Senate, they have succeeded in putting Bayh on the defensive and turning Indiana into a top battleground in this year’s fight for Senate control.