Bad news for Carmike’s management ahead of next Thursday’s shareholder vote on its agreement in March to sell to AMC Entertainment for $1.1 billion (including debt) — creating the world’s largest exhibition chain.

Investor advisory firms Institutional Shareholder Services and Glass Lewis urge clients to vote “no” on June 30, saying that the $30-a-share price is too low. They essentially agreed with arguments made by leading shareholders Driehaus Capital Management (with nearly 10% of the votes) and Mittleman Brothers (with 9.6%) who oppose the deal.

Carmike “has not provided a compelling reason for selling the company at this time for what appears to be a low valuation, particularly given that [Carmike] shareholders will be unable to participate in the potential upside of the combined entity,” ISS says.

It adds that other buyers likely would be interested in the No. 4 exhibition chain. And the fact that its stock traded above $30 for 46 days over the last year “seems to suggest that it would not be such a stretch for the company to achieve this valuation on a standalone basis.”

Glass Lewis also says that the merger “undervalues Carmike’s recent and expected financial performance.” It calls AMC’s offer “opportunistic, seeking to capitalize on the Company’s short-term stock price decline preceding the merger announcement.”

Carmike responded to the reports saying that the deal with AMC “is the culmination of a nearly two-year strategic review process during which no other offers were made.” The price would give shareholders a valuation that is “well above where Carmike’s stock has historically traded or where we expect Carmike’s stock to trade on a standalone basis within any time frame that would be acceptable to us, particularly in light of recent industry-wide downward trends.”

Still, the reports by ISS and Glass Lewis “will undoubtedly make, what we had already expected to be, an extremely close vote on [June 30] even closer,” B. Riley analyst Eric Wold says.

In late May, just 56% of Carmike’s shareholder votes favored its directors, he adds, which reflects “relatively low levels of shareholder satisfaction.”

He believes that AMC could offer more than $40 a share and still make money from a deal — which is why he’s still “confident AMC will ultimately prevail in its acquisition” of Carmike.

Carmike shares in mid-day trading are up 1.6% to $30.60, suggesting that investors believe they’ll end up with more than AMC’s current offer.